Starting control for free-piston units



May 10, 1949. D. E. MEITZLER 2,469,739

swarms comm, Fon REE-ms'ron nuns Filed Aug. 23, 1944 5 Sheets-Sheet 1 INVENTOR May 10, 1949. D. E. MEITZLER 7 2,469,739

STARTING CONTROL FOR FREE-PISTON UNITS Filed Aug. 23, 1944 5 Sheets-Sheet 2 STARTING RELEASE VALVE To |21 12s was I14 I24 I32 I30 I04 I40 EXHAUST I06 MANIFOLD 34 l l2 no 120 STARTING DEVICE FIG. 2

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STARTING CONTROL FOR FREE-PISTON UNITS Filed Aug. 23, 1944 5 Sheets-Sheet 4 INVENTOR May 10, 1949. D. E. MEITZLER 2,459,739

STARTING CONTROL FOR FREE- PISTON UNITS Filed Aug. 23, 1944 5 Sheets-Sheet 5 MASTER CONTROL CUT-OFF YALVE 222 214 TO STARTING 206 I 'SYSTEM COMPRESSED AIR FIG. 5

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Patented M0110, 949 p UNITED" FFICE STARTING CONTROL FOR FREE PISTON UNITS Donald E. Meltzler, Manchester, Conn., assignor to United Aircraft Corporation, East Hartford, Conn., a corporation of Delaware Application August 23, 1944, SerialNo. 550,894

. a 1 This invention relates system for free-piston units.

to a control for a starting.

com (01. 230-56) are always maintained at equal distances from v the center of the engine cylinder by a linkage,

The copending' application of Cooper, Serial I No. 550,875, filed August 23, 1944, issued as Patent 2,439,453, describes a starting system in which the pistons are automatically moved into starting position and then gas is admitted to the air springs to move the pistons rapidly toward each other for starting the unit. If the unit fails to start on the first attempt, the system is adapted to function repeatedly so long as gas under pres sure is supplied to it. A feature of the present invention is a cut-ofi valve for the starting system automatically to stop its functioning while the unit is operating.

A feature of the invention is a control of the gas supply to the starting system to cause the Fig. 1 is a sectional view through the free-piston unit showing the starting system.

Fig. 2 is a diagrammatic view of the starting system. I

Fig. 3 is a diagrammatic view of the cut-on valve and the control valve for the starting system.

- Fig. 4 is a sectional view through the restraining linkage for the pistons. v

Fig. 5 is a diagrammatic view of the master control and the cut-ofl valve.

The unit shown includes an engine cylinder it having reciprocating pistons l2 and M to which compressor pistons l8 and i8 in cylinders 20 and 22 are integrally connected. Sleeves 24 and 28 attached to the compressor pistons complete the reciprocating piston assemblies. The sleeves reciprocate over stationary pistons 28 and 80 and form air spring cylinders.

The piston assemblies are moved apart by the burning of fuel-injected into engine cylinder it through one or more nozzles 82. Air compressed in the air spring cylinders on the power stroke returns the piston assemblies. The assemblies 55 her 83 through a channel 96 communicating with which may include racks 34 and 36, Fig. 4, projecting from the piston assemblies and meshing with a pinion 38 on a shaft 40.

' In take manifold 42 conducts air to intake valves 44 in the heads of the compressor cylinders through which air alternately enters opposite ends of the compressor cylinders. The compressed air leaves the cylinders through discharge valves 46, also at opposite ends of the compressor cylinders and passes into a central scavenge chamber 48 and end chambers 50 and 52. These chambers may be interconnected by a scavenge manifold, not shown. Compressed gas from the chambers enters engine ports '54 and 56 which are uncovered by pistons l2 and M at the end of the power stroke, thereby permitting air to be blown through the engine cylinder. Gas and air in the engine cylinders is discharged through exhaust ports 58 into exhaust manifold 60.

Starting devices 62 for the unit are mounted in the air spring pistons 28 and 30. The devices are similar and only one device will be described in detail. Piston 30 forms a housing having an accumulator chamber 63 in which gas under pressure is collected in readiness for starting. This chamber communicates with the air spring cylinder through a port 64 closed by a poppet valve 66. The stem 68 of this valve is slidable in a guide 10 on a cap 12 which closes the end.

ofichamber 62. Valve 66 closes port 64 by movement toward the storage chamber and is opened by movement .away from the chamber so that pressure of gas within the chamber opens the valve. Pressure of gas in the air spring tends to holdthe valve closed during operation of the unit.

Cap 12 has a bore forming a cylinder 14 which receives a piston 16 on the end of valve stem 88. The inner end of cylinder 14 is connected with the storage chamber by one or more ports 18. A coil spring in the cylinder moves the piston toward valve closing position. A head 82 closes the outer end of cylinder 14 and is held in position by studs 84 extending through both head 82 and cap 12.

A casing 86 on head 82 has a bore 88 in which a plunger 90 is slidable. One end ofbore 88 is closed by head 82, the other end by a cover plate 82. Gas under pressure is admitted to the inner end of bore 88 through a channel 94 in casing 86. With plunger 90 in the position shown, gas entering the inner end of the bore is guided into cham a passage 98 in casing 86, cap 82, and head I2, and the head of piston 30.

Passage 98 intersects bore 88 in alignment with another passage 99 which communicates with the outer end of cylinder I4. Plunger 90 is normally in a position to cut off fluid connection between passages 98 and 99, and has a groove I00, which, when the plunger is moved to the opposite end of its stroke, connects these passages and permits gas to flow through channel 99 into the outer end of cylinder I4, to cause valve 66 to open.

For moving plunger 90 to the inner end of its stroke, casing 86 has a gas inlet passage I02 which is connected by a groove I03 in plate 92 to the outer end of bore 88. When gas under pressure enters this inlet passage, it moves plunger 90 into a position to close channel 96 and to connect passages 98 and 99 to establish fluid connection between chamber 62 and the outer end of cylinder I4. When this occurs, the pressures on opposite sides of piston 16 are balanced and the pressure on valve 66 opens the valve for the escape of gas into the air spring.

In starting the unit, gas under pressure is first admitted through channel 94 until a predetermined pressure is built up in chamber 63 as hereinafter described. After this pressure is reached, gas under pressure is admitted through passage I02 thereby moving plunger 90 to close channel 96 and to cause valve 66 to open. Before this action occurs, the piston assemblies of the 'unit will have been moved to starting position. The sudden inrush of air into the air springs from chambers 62 in starting devices 56 and 58 will move the piston assemblies rapidly toward each other. 7

The starting devices 56 and 58 may be controlled by an automatically operating valve I04 which controls the admission of gas under pressure to channel 94 and passage I02. Valve I04 includes a casing I06 having a bore in which a valve plunger I08 is mounted, the plunger being normally held in the position shown by a spring III]. The tension of spring II8 ma be adjusted by a nut II2 engaging threads in casing I06 to control the pressure in chamber 62 at which the starting device operates.

Casing I06 has an inlet port II4 connected to a source of gas under pressure, and an outlet port II6 connected .by a conduit II8 to channel 94. Another outlet port I20 spaced from port H6 is connected by a conduit I 22 to passage I02. In the normal position of plunger I08 a groove I24 in the plunger connects ports H4 and II6 and another groove I26 establishes fluid connection from port I20 to a chamber I21 at the end of easing I06. When plunger I08 is shifted to the other end of the stroke, as limited by a. threaded ring I28, groove I24 connects inlet port II4 with port I20, and another groove I30 connects port I I6 to a vent port I32.

For moving plunger I08, the end of easing I06 has a nut I33 with a through passage I34. Nut I33 clamps a bushing I35, the end of which forms a valve seat engaged by the end of plunger I08. Passage I34 is connected by a branch conduit I36 to conduit I38 which connects with inlet port II4. Branch conduit I36 has an adjustable throttle valve I40 which can provide a restriction greater than any restriction from conduit I38 to chamber.63. When the desired pressure is developed in chamber 63, the pressure in passage I34 acting on the end of plunger I08 moves the plunger against the action of spring IIO to connect-port I20 to inlet port II4 for pro- .4 curing opening of valve 86 for starting the unit.

A small bleed passage I40 in casing I06 provides fluid connection from the end of plunger I08 to groove I30 which connects with vent port I32. This permits gas leaking past the end of plunger I08 to be vented so that the plunger will not bemoved from the position shown until the desired pressure'has been built up in chamber 62.

A passage I44 in casing 86 connects passage 99 with groove I03 in cap 92 and is closed by a check valve I46. After-the starting unit has operated and conduit I22 is vented by plunger I08 returning to the position shown, gas at the right of piston I6 in cylinder I4 may escape past valve I46 so that piston I6 may move into a position for closing poppet valve 66.

The piston assemblies may .be automatically moved to the outer ends of their stroke before the starting devices operate. The structure is the sam for each piston assembly and only one of the structures will be described. Compressor piston I8 has projecting concentric sleeves I48 and I49, Fig. 3, connected at their outer ends to form a plunger I50 sliding in an annular space I5l between a sleeve I52 and a smaller sleeve I53 mounted within the unit. Only one plunger is shown, but, for purposes of balance, two oppositely placed plungers may be advantageous.

Gas under pressure is admitted to the left hand end of space I5I to move the piston assembly of which piston I8 is a part. A valve casing I54 has a sliding plunger valve I56 held in the position shown b a spring I58. In this position gas entering an inlet port I60 passes around a groove I62in valve I56 to an outlet port I64 connected by a conduit I66 to the end of a bore I88 in a casing I10 at the end of sleeve I52. From bore I68 gas under pressure passes through a channel In in casing I10 and a channel H4 in head I'I5 on sleeves I52 and I53 to the inner end of space I5I. Gas entering the end of this cylinder moves plunger I50 to the right, carrying with it the attached piston assembly and moving the piston assembly into starting position.

As plunger I50 moves to the right, it uncpvers a port I'I6 connected by a conduit I'I8 to a passage I in a cap I8I in the end of casing I54. Gas entering this passage acts on the end of valve plunger I56 which is in the form of a valve engaging a seat I82 in a ring I83 at the end of passage I80 and moves the plunger to the left against the force of spring I58. Inlet port I60 is then connected by groove I62 to a port I84 which is connected by conduit I38 to the starting release valve.

When valve plunger I56 is moved to the left, port I64 is connected by a groove I86 in plunger I56 to a vent port I88 causing a pressure drop in conduit I66 and permitting a check valve in the form of a plunger I90 in bore I68 to be moved by a spring I92 to close passage I'I2.

After the engine is started, plunger I50 acts as a. pump forcing gas under pressure through passage II4 past a disc valve I94 and through a channel I96 to a conduit I98 leading to the left hand end of easing I54. Pressure entering the casing acts on the end of valve plunger I56 to return it to the position shown. While gas under pressure is being admitted to the balance pump, valve I90 is' moved into a position to close passage I96. This passage is opened upon return of valve I90 to the normal position shown.

The starting system above described is claimed in the-copending application .oi cooper, Serial No.

550,875, filed August 23, 1944. The present invention relates to the arrangement by which the includes a casing 262 having an inlet port 264" connected to a source of gas .underpressure and an outlet port 266 connected by]. conduit 268 to port I66 of easing I64. Between ports 264 and 266 is a valve 2" heldagainst its seat by a spring H2 and normally preventing gasirom passing between the ports. The valve 216 has a stem 2, the end of which engages a lever 2" on a shaft 2". A projecting arm 226 on lever 2l6-engages the end of a piston 222 in a bore 224 in casing 262. Downward movement of the piston (upward movement in Fig. 5) moves the valve stem to open valve 6 In a bore 228 also in casihg 262 is a valve plunger 228 normally held in the position shown by spring 236 and moved downwardly (upwardly, Fig. 5) by gas under pressure entering port 232 to uncoverv a connecting port 234 between bores 224 and 226. When port 284 is uncovered pressure entering bore224 moves the piston down to open valve M6 and permit the starting device to operate.

Port 232 is connected by a conduit 236 with a master control 238 which varies the pressure in conduit 236 in accordance with the spacing of theactual outer end of the piston stroke from the extreme outer end position of the piston. As shown mm. 5 this control is actuated by a cam 249 on shaft 46. Since the pinion" on thisshaft is oscillated directly from the pistons the movement of cam 246 is proportional to the piston stroke.

Fluid under pressure from a constant pressure source enters a passage 242 in a casing 244 forming a part of the control 238. Passage 242 is connected to the source by. a conduit 246. Passage 242 intersects a bore 248 adjacent its outer end and a throttling screw 266 controls the rate of flow into bore 248. A branch passage. 252 from passage 16 connects with a port 254 in bore 248. A plunger 256 in bore 248 has a groove 268 which connects a port 266 alternately with port 254 or with a port 262. Port 266 is connected by a passage 264 to the inner end of bore 248. Port 262 'is connected by a channel 266 in casing 244 and in an adjacent casing 268 to the inner end of a bore 216 in casing 268.

A piston 212 in bore 216 is moved to the right by a calibrated spring 214. A plunger 216 extends through the piston and carries on its projecting end a push rod 218. This rod has a roller 286 held against a, cam 246 by a spring 282. Plunger 216 has a central passage 284 connecting with spaced grooves 266 and 286 in the plunger. Groove 286 aligns with openings 236 in a sleeve 292 carried by piston 2-12, and groove 288 is adapted to be uncovered by the end of sleeve 292 as the plunger is moved to the right by cam 246% the piston approaches the outer end of its stroke.

Fluid under pressure from the right-hand end 70 of bore 248 enters the outer end of bore 216 through a connecting channel 234 moving piston 212 against the action of spring 214. As plunger 216 is moved to the right by cam 246 the groove 288 is-uncovered by sleeve 282 to permit discharge "(6 of fluid from the right-hand end of bore 216. The pressure in the outer end of bore 216 varies in accordance with the compression oi spring 214 and as the piston stroke becomes shorter the.

piston 2 12 moved inward. increasing the spring varyin; the same manner. In this way, the pressure in conduit 266 which is connected by a channel 286 to theinner end of bore 248 is proportional to the spacing of the actual end oi the piston stroke from the extreme outer position 01' the piston. Changes in pressure in conduit 266 will be proportional to changes in the outer end position of the piston stroke. The pressure and change in pressure in the conduit control the operation of the cut-oil valve.

The outer end 01' plunger 216 may reciprocate in a chamber 298 whichmay be connected by a conduit 366 to the conduit 662, connected by passage 364 to the inner end 01' bore 216. A bellows 366 connected with passage 264 may be used to reduce pressure fluctations in the control.

In operation, when the unit is stopped, the

engine pistons are between the ends of their strokes causing a high pressure to be indicated, by the master control, Fig. 5.. This high pres- .sure in conduit 236 acts to hold plunger 228 in the position shown, permitting entry of fluid to bore 224 and moving piston 222 into the up position of Fig. 5 so that valve. 2| 6 is open to admit starting air to the starting system. As soon as the unit is operating, the pressure in conduit 266, as indicated by the master control, drops, thereby cutting oii the flow of fluid under pressure to bore 224 and permitting fluid from this bore to exhaust through a passage 868 in plunger 226. The piston 222 then moves downward, Fig. 5, thereby closing valve 2l6 and cutting 01! the supply of starting air to the starting system. As a result, the operation of the starting system is under the control of the free-piston unit so that the starting system, which is completely automatic, will be supplied with starting and cranking air while the unit is not running to cause the starting system to operate for starting the unit. Immediately the unit begins its operation themaster control pressure drops, the cut-oi! valve is closed and the starting system remains inoperative unless the unit stalls. The air spring pressures .and the other pressures acting on the piston assembly cause the piston assembly to come to rest, when the unit stalls, at a point spaced substantially from the outer end of the piston stroke, thereby producin ahigh pressure indication by the master control which will cause the c'ut-ofl' valve to open.

It is to be understood that the invention'is not limited to the specific embodiment herein illustrated and described, but may be used in other ways withoutdeparture irom'its spirit as I off valve for controlling the supply 01' fluid under pressure to said system, in combination with a stroke indicator operative during the operation of the unit for indicatingthe end positions of successive piston strokes, and means under the control of said indicator for operating the cut-off valve to close it during operation of the unit.

2. A free-piston unit having a cylinder, 2. piston reciprocating in the cylinder, a fluid pressure actuated starting system for the unit, and a cutoff valve for controlling the supply of fluid under pressure to said, system, in combination with a hydraulic system, a hydraulic stroke indicator having means for adjusting the pressure in the hydraulic system in accordance with changes in the end positionof the piston strokes, and means for actuating said cut-off valve in response to changes in pressure in said hydraulic system.

3. A free-piston unit having opposed pistons, a cylinder in which said pistons reciprocate, air springs for each piston, and a fluid pressure actuated starting system for said unit including fluid pressure actuated means for moving the pistons into starting position, and means rendered operative by movement of said pistons into starting position for supplying fluid under pressure to said air springs for causing said pistons to move simultaneously for starting, in combination with a control system, means responsive to changes in the location in the ends of successive piston strokes during operation of the unit for procuring changes in the pressure in the control system, and means responsive to changes in the pressure in the system for controlling the supply of fluid under pressure to said starting system.

4. A free-piston unit including a cylinder, a piston reciprocating in the cylinder, and starting means for the unit, including means for moving the piston into starting position, means for imparting a stroke to the piston from starting position, and means responsive to said piston movement into starting position for settingsaid other means in operation, in combination with means for stopping the operation of said starting means and means responsive to reciprocation of the piston in the cylinder during operation of the unit for actuating said stopping means.

5. A free-piston unit including a cylinder, av

piston in the cylinder, and fluid pressure actuated starting means for the unit, including means for moving the piston into starting position, means for imparting a stroke to the piston from starting position and means responsive to said piston movement into starting position for setting said other means in operation, in combination with means for cutting ofi the supply of fluid under pressure to said starting means, and means responsive to reciprocation of the piston in the cylinder during operation of the unit for actuating said cut-off means.

6. A free-piston unit including a cylinder, a piston in the cylinder, and a fluid pressure actuated starting system including means for moving the piston into a position for starting, other means for imparting a stroke to the piston, both of said means being actuated by fluid under pressure, and means responsive to said piston movement into starting position for setting said other means in operation in combination with means for cutting off the supply of fluid under pressure to said system, and means responsive to successive reciprocations of the piston during normal operation of the unit for actuating said cut-oi! means.

DONALD E. MEITZLER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS OTHER REFERENCES Ser. No. 418,666, Mullejans .et al. (A. P. 0.), published June 15, 1943. 

